Why Does My Toilet Randomly Run For A Few Seconds?

Matthew Mountain
by Matthew Mountain

If you’ve experienced “phantom flushing” before, then you know this phenomenon is startling and perplexing, at first, but eventually incredibly annoying. The phantom flush is a common toilet malfunction, and a range of things can cause it.

This article explains the problem in detail and offers numerous solutions as well. If you don’t have the skills, know-how, and/or tools available to fix this problem on your own, then you should get help from a professional plumber.

If your toilet is flushing randomly, it’s most likely because the tank is leaking. The tank could be leaking because of a malfunctioning flapper. Specifically, the flapper isn’t able to make a tight seal, which means water leaks through. A leaking tank will trigger the filling mechanism, and this is what causes the phantom flush.

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How a Toilet Is Supposed to Function

These days, toilets are incredibly important fixtures that human beings can’t live without. But how are these fixtures able to generate a powerful, suctioning flush again and again? Here’s a bare-bones explanation of how a toilet is supposed to function:

When the toilet’s exterior lever is pressed, an interior component known as the float valve lifts up, releasing water into the bowl. While this is happening, the water and waste in the bowl are being sucked down a pipe where they’ll eventually end up in the local sewerage system.

As the bowl empties, the flapper will slowly sink, to the point where it eventually rests on a component called the flush valve. As the flapper slowly reduces the amount of water entering the bowl, the toilet’s fill valve—otherwise known as the ballcock—refills the toilet’s tank so it’s ready to be flushed again.

This isn’t a complicated process, but because numerous components are involved, there’s always a chance that something will go wrong and render the toilet inoperable, either for a short period or for good. In general, randomly flushing toilets aren’t those that are on their last legs, so repair is a much more common solution than replacement.

What’s Causing the Toilet to Run Randomly?

While there are a few common causes for a randomly flushing toilet, most often this problem is caused by the toilet’s flapper not being able to hold a good seal. Seal-related problems are often due to sediment buildup, but prolonged hard water exposure can also cause the flapper to not seal correctly. The other common culprits are briefly explained below.

The Flapper Chain Wasn’t Installed Properly

Since the flapper chain pulls the flapper up and lowers it down, it’s considered a critical component in the flushing process. Therefore, if the chain is not properly attached to the flapper, then the flapper could malfunction.

A similar problem is when the flapper chain is too long or too short. An incorrect chain length can prevent the flapper from sealing the hole properly. And as was said before, a compromised seal can often lead to random flushing.

There’s a Problem With the Fill Valve

If there’s a problem with the fill valve, then the toilet may flush randomly. Since the fill valve is responsible for filling the tank after a flush, a malfunction could cause the tank to continuously fill with water. If this happens, the toilet will continue to run—in other words, it’ll keep flushing.

If the fill valve damage is minor—like a small leak—then the consequence is often random flushing. A major leak, on the other hand, is much more likely to cause continuous flushing, as the system is constantly acting to replace the leaking water.

Too Much/Not Enough Water

If the toilet is not holding the proper amount of water, i.e. it’s either too full or too empty, then random flushing could be a consequence of this. The toilet water should always be above the fill valve, and generally there should be about 1 to 2 inches (or 2.5 to 5 cm) of distance between the water’s surface and the fill valve.

A properly functioning toilet will fill with the correct amount of water after each flush, so if this isn’t happening, there may be another problem that needs addressing before you can address the random flushing. Or it could be that this problem is causing both issues.

The Toilet’s Handle Is Sticky or Broken

If the toilet’s handle is sticky—as in it doesn’t press and release smoothly—then this can cause random flushing. Pressing the handle is what initiates the flushing process. Therefore, if the handle doesn’t return to its default position after being pressed, then water can’t enter the tank as it’s supposed to.

A sticky handle is more associated with random flushing whereas a handle that sticks, and doesn’t go back, after flushing is associated with continuous flushing.

Addressing the Problem

If your toilet keeps randomly flushing, eventually this will become quite annoying. And aside from being annoying, this malfunction can also be costly, especially if you let the problem go on for too long. Below are some steps you can take to remedy a randomly flushing toilet.

Keep in mind that a professional plumber may follow a different process when addressing this problem. The steps outlined here are intended to give you a general idea of how the random flush problem is fixed, but in no way is this an exhaustive guide for random flushing toilet repair.

Step One: The first thing you’ll need to do is lift the lid of the toilet off so you can access the tank.

Step Two: Next, look for the lift chain. If this chain is too long or too short, adjust it so that it’s a suitable length. Now tighten or loosen the chain accordingly so there’s at least a half-inch of slack at the midpoint.

Step Three: The next step is locating the float ball. If you find that the float ball is cracked, then you’ll need to replace this. Turn the ball counterclockwise until it’s released from the threaded rod. Now put the new ball where the old one used to be and tighten it to ensure it’s secure. If after you screw down the float ball you find it’s too loose, simply re-fastened it until you reach the desired tightness.

Step Four: If the float height needs to be adjusted, do this. Remember that if the water doesn’t rise high enough to shut off the fill valve after flushing, the system will continuously run.

Step Five: Now it’s time to clean the flapper thoroughly to ensure that there’s no sediment buildup. In order to access this, you’ll need to turn off the water and then drain the toilet bowl by flushing it. To further get rid of toilet sediment buildup, take an emery board and rub it across the edges of the seat.

Step Six: Once all the preceding steps have been taken, reinsert the rubber stopper, turn the water back on, and flush the toilet a few times. If after this the toilet does not flush again on its own, you’ll know the problem has been solved.

Calling a Pro

Generally speaking, repair work like this should not be handled DYY. Instead, you should get help from a professional plumber in your area when you want to solve the random flush problem.

How This Problem Affects the Water Bill

If your toilet runs when you’re not using it, even if this happens randomly, then you can expect your regular water bill to increase. It may come as a surprise, but random flushing can waste hundreds of gallons of water in a single week.

For this reason, when you identify that your toilet is flushing randomly, you should address this problem sooner rather than later, either by yourself or by hiring a professional plumber. The longer you let this problem go on, the more you’ll be paying for inaction.

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Related Questions

Since toilets are arguably the most important bathroom fixture, it makes sense that a lot of homeowners want to know everything they can about these fixtures. Some of the frequently asked questions that relate to this article’s topic are answered below.

What’s a good flapper replacement?

Try the Korky 100BP Ultra High-Performance Flapper. This flapper is often regarded as the best, and its universal design means you can use it with the vast majority of toilets out there now.

It’s flexible and made of long-lasting rubber, so you can count on this item to ensure a tight seal. It’s also reasonably priced and can be easily purchased through Amazon. For more flapper options, consult this post.

Could the refill tube be causing the random flushing?

Yes, random flushing could be caused by a malfunctioning refill tube. The refill tube may be too long or it may need to be repositioned—either problem can cause the system to pump water into the bowl unnecessarily. Make sure that the tube is positioned in the right spot, i.e. above the opening of the overflow.

Final Note

In the end, a toilet that flushes randomly may seem tolerable, but this issue is often the symptom of a problem that will eventually lead to more significant issues. For this reason, it’s best to get the problem addressed right when you notice it. A quick response will ensure your toilet doesn’t sustain costly damage.

Matthew Mountain
Matthew Mountain

Matt loves everything DIY. He has been learning and practicing different trades since he was a kid, and he's often the first one called when a friend or family member needs a helping hand at home. Matt loves to work with wood and stone, and landscaping is by far his most favorite pastime.

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